An accidental avalanche arises from general causes taking effect fortuitously.
The general causes are:—
1. A quick rise in the temperature.
2. A sudden fall of the barometer.
3. A change of wind.
4. A fresh fall of snow.
5. Slopes of a certain angle and conformation.
6. Differences of density, moisture, and consistency in superposed layers of snow.
A study of the statics of snow is the royal road to the understanding of avalanches.
On a slope snow is in a state of more or less pronounced instability.